Reducing the excretionof NH3 by livestock

Combating acidification

The intensification of production which, over recent decades, has led to the development of intensive husbandry – particularly for pig and poultry – as well as its concentration in major European areas of production, have gradually increased the phenomena of pollution, especially by nitrogen. Nitrogen and its by-products (nitrates, nitrites, ammonium hydroxide, etc) come from animal slurry which is spread over the fields. In some areas, this has led to amounts which exceed regulations in soil, water and the air. This is the reason why some countries – and more recently, the European Union (Directive 96 / 61 / EC of September 24th, 1996) - have implemented regulations which aim to limit and reduce nitrogen excretion in the environment.

The nitrogen contained in animal droppings comes predominantly from feeds. Nitrogen which is mainly ingested under the proteins form is metabolized by animals to assimilate the amino acids which are necessary for their growth and metabolic functions. In this process the proteins which are not absorbed by the animals and amino acids which are in excess are catabolised and lead to an increase in nitrogen excretion.

The most effective way to avoid these excesses therefore involves limiting them at source, in other words, in the feeds. In contrast to curative measures (exportation and processing of liquid manure, compost, improvement of infrastructures), the preventive measures take direct action against the source of the pollution. Thus, lowering the dietary crude protein (CP) level is an extremely effective strategy to reduce nitrogen pollution by animals. Studies on this subject have shown that lowering CP content in feed for pig or poultry by 1 point makes it possible to reduce the amount of nitrogen excreted by animals by about 10% (Table 1).

These feeds make it possible to develop European cereals usage whilst reducing the quantities of nitrogen excreted in the environment by livestock. It can therefore be estimated that an increase of 5 points of cereal inclusions allows reducing nitrogen excretion by pig and poultry by 10%.

Feed-use amino acids play a vital role in the elaboration of dietary formulas with low CP content. In fact, whilst reducing nitrogen content under the proteins form, they make it possible to maintain the content of indispensable amino acids in such a way that the animal's requirements are met and performance maintained. The possibilities of lowering the content of feed proteins are therefore directly dependent on the availability of amino acids. Thus, with the amino acids which are now commercially available and particularly the one produced by Ajinomoto Animal Nutrition Europe (L-Lysine, L-Threonine, L-Tryptophan and L-Valine) it is possible to reduce the amounts of nitrogen excreted into the environment by half.

The development of feed formulas with increasingly reduced CP content and the generalization of their use will make it possible to develop a sector of animal production which is respectful of the environment.